An 11-year-old Quarter Horse mare from Salem County has tested positive for West Nile virus (WNV), the first case in New Jersey this year. The animal began showing signs of illness on Aug. 4 and was subsequently euthanized.

"We want to remind people to vaccinate their horses against mosquito-borne diseases," said New Jersey Secretary of Agriculture Douglas H. Fisher. "Horse owners should contact their veterinarians to protect their animals from these preventable diseases." The American Association of Equine Practitioners’ vaccination guidelines for both WNV and Eastern equine encephalitis (EEE), another important mosquito-borne disease, are available online.

Clinical signs for WNV include flulike signs, where the horse seems mildly anorexic and depressed; fine and coarse muscle and skin fasciculations (twitching); hyperesthesia (hypersensitivity to touch and sound); changes in mentation (mentality), when horses look like they are daydreaming or "just not with it"; occasional somnolence (drowsiness); propulsive walking (driving or pushing forward, often without control); and "spinal" signs, including asymmetrical weakness. Some horses show asymmetrical or symmetrical ataxia (incoordination on one or both sides, respectively). Equine mortality rate can be as high as 30-40%.

A viral disease, EEE affects the central nervous system and is transmitted to horses by infected mosquitoes. Its fatality rate in horses is 75-95%. The course of EEE can be swift, with death occurring two to three days after onset of clinical signs despite intensive care. Horses that survive might have long-lasting impairments and neurologic problems. Clinical signs of EEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures